1. Technical Field
The present invention relates generally to cooling printed circuit board components and in particular to an apparatus employing a mixed convection airflow mechanism for cooling vertically stacked printed circuit boards.
2. Description of the Related Art
With microelectronics technology steadily increasing integrated circuit (IC) chip density and the density in which such circuits are mounted onto system planar printed circuit boards (PCBs), cooling issues are becoming increasingly critical to design of large-scale data processing systems. Electronic systems containing densely packaged components typically utilize fans or blowers for forced-air cooling.
Systems for cooling electronic components mounted within a computer housing may provide circulation of a fluid coolant medium (usually air) by means of a distributed fan system adapted to circulate air throughout the housing. In concert therewith, or in the alternative, strategically positioned chambers, ducts, and baffles may be employed to distribute the forced-air coolant medium throughout the housing.
Current requirements for compact, lightweight electronic packages, containing, for example, a large number of closely spaced or stacked electronic circuit boards have not been fully satisfied by existing systems either because such systems provide an insufficient coolant flow to particular components due to such components being blocked from the coolant flow path by other components or boards, or because of the substantial additional hardware required to implement effective ducts and baffling structures.
A system and apparatus addressing some of these problems is described in U.S. Pat. No. 4,399,484 issued to Mayer. The cooling system described therein employs a forced air technique wherein a blower is utilized to drive a forced convection airflow generally perpendicular to the planar surfaces of a set of horizontally stacked circuit boards. The circuit boards have multiple airflow passages defined therethrough to facilitate passage of the coolant flow through the stacked boards. The forced-air system described by Mayer addresses some of the foregoing problems relating to cooling blocked components while minimizing cooling support infrastructure. However, implementation of such a system would result in uneven heat dissipation, with the aft-stacked boards (i.e. boards furthest from the blower source) receiving a disproportionately ineffective convection stream. Specifically, the speed of the coolant flow is greatly diminished following impingement with the first one or two boards thus reducing the convection heat removal effect. In addition, the forced air convection flow becomes heated as it sequentially passes through each successive board, thus greatly reducing the effectiveness of the air medium as a convective heat removal medium.
Therefore, a need exists for a need for an improved PCB cooling system that overcomes the aforementioned problems. The present invention addresses these and other needs unresolved by the prior art.